Behavior of the Germ-cells 179 
Buller’s experiments with the eggs of sea urchins and starfish 
have given important results. He pointed out that spermatozoa 
accumulate around immature eggs, and also around mature eggs 
that had been killed in osmic acid and then thoroughly washed 
in sea water. In this case it is highly improbable that any attrac- 
tion could exist. The results are due to those spermatozoa that 
accidentally run into the membrane of the egg, remaining stick- 
ing there as a result of some physical property of the jelly or of 
some reaction on the part of the spermatozoédn. Buller showed 
by means of the following experiment that the eggs do not se- 
crete an attracting substance. Eggs were allowed to stand in a 
little water from two to twelve hours. Capillary tubes were then 
filled with this water and placed in a drop of sea water containing 
the sperm. No collecting of spermatozoa around the ends of the 
tube was observed. He alse tried other substances in the tubes, 
viz. salts, sugars, ferments, and alcohol, etc., but no evidence 
of their action in attracting the spermatozoa was observed. 
Buller thinks that the spermatozoa are sensitive to contact, 
hence on coming into contact with the membrane bore into it. 
The spermatozoa swim in spirals in the water, but on entering 
the jelly they take a straight course, which in most cases will 
bring them into contact with the egg, although, if they should 
enter quite obliquely they may bore through the periphery of the 
membrane and pass out again on the other side. Thus even 
after entering the membrane, there is no evidence that the egg 
attracts the spermatozoa toward itself. 
On the other hand it has been shown by von Dungern that the 
egg and its membranes may contain and even give off substances 
that act in some cases injuriously on the spermatozoa of other 
species. The egg of the starfish, Asterias glacialis, contains a 
substance that acts as a poison on-the spermatozoa of the sea 
urchins — Echinus or Spherechinus. The minimal lethal dose 
for sperm mixed with two cubic centimeters of sea water varies 
with different individuals between the limits of g35 to ggoq 
parts forhalfan hour. The same poison is found also in the skin 
of the starfish. Cross-fertilization of the eggs of this starfish by 
